Effect of nest environment on olive ridley (Lepidochelys olivacea) hatchling fitness

Student name: Ms Pusapati Chandana
Guide: Dr Sudipta Chatterjee
Year of completion: 2019
Host Organisation: Centre for Ecological Sciences, Indian Institute of Science, Bangalore
Supervisor (Host Organisation): Dr Kartik Shanker

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Abstract:

Nest environment plays an important role in influencing hatchling phenotype. Efficient locomotion is necessary for hatchlings to overcome predators before and after they enter the sea. Increasing global temperatures could thus, potentially threaten the resilience of populations by causing detrimental changes in hatchling size and fitness. Temperatures between 29°C and 32°C were found to be optimal for the successful development of embryos. Temperatures above and below this range result in significant changes in hatchling phenotype. In species such as loggerheads and green turtles, previous studies used constant incubation temperatures to investigate the effect of temperature on hatchling fitness and found reduced size, crawl speed, righting ability and swimming performance in hatchlings incubated at temperatures below 27°C and above 32°C. However, the results of studies carried out at constant temperatures cannot be applied to natural nests, where temperature fluctuations occur on a daily basis. Studies on olive ridley turtles have been limited and hatchling physiology has been poorly studied. A substantial gap, therefore, exists in our understanding of temperature-induced changes in morphology and fitness of hatchlings, especially for olive ridley turtles. It is important to understand the extent and degree of influence of the nest environment, especially temperature, on hatchling morphology and fitness. Here, I examined temperature-induced differences in morphology and fitness of hatchlings produced at two hatcheries, Rushikulya and Chennai, by analyzing the relationship between temperature and various hatchling phenotypic variables. It was found that hatchling size (R² = 0.81, p <0.001) and fitness (R² = 0.76, p <0.001) were significantly influenced by nest incubation temperature. Higher incubation temperature led to smaller hatchling size which in turn was correlated with lower fitness. Nest incubation temperature also had a direct effect on hatchling fitness regardless of hatchling size. Therefore, increasing sand temperatures may produce hatchlings that are smaller in size with poorer fitness. This might have an effect on their recruitment and survival rate, thus influencing population dynamics and resilience to climate change.

Keywords: Olive ridley sea turtles, Hatchling fitness, Morphology, Temperatureinduced, Rushikulya, Chennai